Conventional bursters are well known in the art, and are widely employed to separate the successive forms of stationery from a continuous web of stationery. Bursting is normally accomplished by feeding a web of paper or stationery through a first pair of input or feed roller which are rotated at a first rate and then feeding this web into engagement with a second pair of output or draw rollers rotating at a much greater rate than the input rollers, so that the leading edge of the web is gripped and yanked forward to tear the web laterally along perforations across the web. Commonly, some type of bar or rolls are provided at the location of the perforation to be torn or separated, as shown for example, in U.S. Pat. Nos. 2,803,304 and 3,161,335. An improvement in this respect is shown in U.S. patent application Ser. No. 922,744 by the present inventor. In accordance with this improvement, the speed of rotation of the output or draw rollers may be reduced to minimize the noise of bursting operations.
The rollers normally employed in bursters are formed of a rubber composition which as a practical matter can only be manufactured with some variation in dimensions. Thus it has been found necessary in the prior art to provide "flats", upon one of the feed rollers at least, in order to periodically release the grip thereof on the web so that the web will not be progressively fed at a small angle through the burster. With flats provided on an input roller, it is then also important to provide flats on an output roller, in order that the output rollers will not grip and yank the web forward when the web is not held by the input rollers. Under the latter circumstance, failure to separate a form or sheet from the web might occur or tearing of the web at some location other than the perforation might result.
With the provision of flats or planar surfaces on a roller of each pair of rollers in a burster, it then becomes necessary to rotate the pairs of rollers in synchronism and this causes certain problems when the physical separation of the pairs of rollers must be varied. It is common to provide bursters with the capability of bursting at adjustable distances along the web in order to accommodate forms or the like of different sizes. Conventionally, bursters are provided with relatively complicated mechanical motion drive means in order to satisfy the requirement of synchronous roller rotation and adjustable separation between pairs of rollers.
The present invention provides an improvement in bursters which materially simplifies the mechanical structure thereof.